The present invention relates to electrical connectors, and specifically to electrical connectors having closely spaced contacts and printed circuit boards where interference from crosstalk in the connector is a concern.
Various electrical connectors are known for use in the telecommunications industry to transmit voice, data, and video signals. It is common for some electrical connectors to be configured to include a plug which is connectable to a jack mounted in the wall, or as part of a panel or other telecommunications equipment mounted to a rack or cabinet. The jack includes a housing which holds a plurality of closely spaced contact springs in the appropriate position for contacting the contacts of a plug inserted into the jack. The contact springs of the jack are often mounted to a printed circuit board, either vertically or horizontally. An RJ45 plug and jack connector system is one well known standard including closely spaced contacts.
Crosstalk between the contacts and circuit pathways in telecommunications connectors is a concern. U.S. Pat. Nos. 5,299,956 and 5,700,167 are examples of various connectors including jacks and plugs which attempt to address the problem of crosstalk in the circuit board. It is desired to improve performance of the electrical connectors, such as an RJ45 connector, where crosstalk problems increase as higher frequencies are transmitted through the connector.
Most of the crosstalk problems occurring in a connector, such as an RJ45 connector, is mainly caused by the plug. This crosstalk is produced by the non-periodic or random discharges of crosstalk energy due to the imbalanced capacitance and/or inductance in the plug and the contact springs of a jack. RJ45 types of connectors are mainly used with balanced twisted pairs of conductors or wires. There is no grounding to shield the crosstalk energy.
One of the known techniques commonly used to solve the crosstalk problem in a connector is to balance the capacitance on the printed circuit board or on a substrate of the connector to minimize or eliminate the leaking energies from the unbalanced capacitance. The known method of reducing crosstalk generally includes forming of a capacitor by using two parallel conductive lines or wires and inducing electro-magnetic field to compensate the lesser field produced by the capacitive imbalance in the plug. This method is often referred to as capacitance balancing or capacitive compensation. The known compensation technique is applied at the nearest unbalanced components, which are the contact springs of a jack and the mated RJ45 plug. This technique is very useful for the TIA/EIA category 5 and Enhanced category 5 (5E) connector. However, the crosstalk performance of these connectors is rated only up to 100 MHz. Higher frequencies are in demand in the telecommunication and data transmission industry. The TIA/EIA category 6 connector standards have been proposed to meet the demand. Under the proposed category 6 standards, the connector is required to meet the crosstalk specifications up to 250 MHz, which is about 150% more bandwidth than the category 5""s.
In order to meet this specifications, additional compensations or additional parallel conductive lines are needed to be placed on the circuit board at the nearest unbalanced components. It has been found that capacitive compensation only worsens the directivity or equal-level of the far-end crosstalk (FEXT) of the connector because the capacitor formed by two conductive lines has an inductive effect which is not accountable for. Also, it has been found that the additional compensation has a reverse capacitive effect on the near-end crosstalk (NEXT) of the connector. Generally, the far end and the near end are defined according to the two ends of the printed circuit board. The end to which signals are being injected is the near end. The opposite is the far end.
In addition, the natural crosstalk characteristic for short transmission lines, i.e. xe2x88x9220 dB per frequency decade, will be lost if the connector is heavily compensated. This natural crosstalk characteristic is generally required to be maintained in order for a connector to meet the category 6 crosstalk specifications.
Accordingly, the known compensation technique is either insufficient to compensate the crosstalk, or problematic by overcompensating for the crosstalk. The known compensation technique has been considered ineffective when applied to the development of a category 6 or a category 6 type of connector, and particularly, it is unable to meet the crosstalk specifications up to 250 MHz.
Thus, there is a need for a connector including an improved crosstalk compensation technique for a printed circuit board. Further, there is a need for a connector with balanced capacitance and/or inductance on the printed circuit board to minimize or eliminate crosstalk in the connector.
The present invention provides a method of compensating crosstalk for a printed circuit board of a connector. The present invention also provides a connector including such crosstalk compensation method.
The present method of compensating crosstalk for a printed circuit board includes a forward compensation process and a reverse compensation process. The forward compensation process compensates capacitively for the unbalanced capacitance in the plug by forming capacitors, for example, using the parallel conductive lines or wires on the printed circuit board. The reverse compensation process can be used to compensate the unbalanced capacitance and inductance caused by the forward compensations in the same pair combination of the connector. In other words, the reverse compensation negates the forward compensation at the far-end of the printed circuit board by forming capacitors, for example, using the parallel conductive lines or wires, at the far-end of the printed circuit board.
In one aspect of the present invention, the method of compensating crosstalk in a connector arrangement includes: providing a plurality of pairs of conductors on a printed circuit board, the pairs of conductors connecting to respective front and rear terminals, each pair of conductors including a ring conductor and a tip conductor, and the ring and tip conductors being substantially disposed in parallel to control the transmission line impedence; sending electrical signals between the front and rear terminals; generating forward-compensating capacitance, induced between two of the pairs of conductors, proximate the respective front terminals by providing a first capacitor between a first conductor of the first pair and a second conductor of the second pair and providing a second capacitor between a second conductor of the first pair and a first conductor of the second pair; and generating reverse-compensating capacitance/inductance to compensate the unbalanced capacitance/inductance induced between the two pairs of conductors by the first and second capacitors at the front terminal. The reverse-compensating capacitance/inductance is disposed proximate the rear terminals by providing a third capacitor between the first conductor of the first pair and the first conductor of the second pair and providing a fourth capacitor between the second conductor of the first pair and the second conductor of the second pair.
Accordingly, unbalanced capacitance/inductance, induced between the two pairs of conductors on the printed circuit board is compensated by the first, second, third, and fourth capacitors.
In one aspect of the present invention, the capacitance/inductance of the same two pairs of conductors is compensated at the opposite terminals in the reverse compensation process.
In another aspect of the present invention, the forward-reverse compensation technique can also be applied to minimize or eliminate crosstalk induced between any other combinations of two pairs of conductors on the printed circuit board.
One of the advantages of the forward-reverse compensation technique is that by reversing the compensations of ones at the opposite terminals, both the far-end crosstalk performance and the near-end crosstalk performance are improved. The inductance effect resulted from forming the capacitors at the front terminals of the printed circuit board of the connector is also balanced.
These and various other features as well as advantages that characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.